Looping for input data

I am a new user for matlab programing and I made the simple following program and I need to make a loop for intering data with index i as following:

% Length of variable x and the Number of Entered data n

   x =0:10; 

%===================================================
% Entered data

for i= 0:10
    i=i+1;
x(i)=input('Enter measured point: ');
z(i)=input('Enter depth: ');
R(i)=input('Enter Raduis: ');
rho(i)=input('Enter density: ');

end

   gz(i)=G*4*pi*R.^3/3.0*z*rho./(x.^2+z.^2).^1.5;

%===================================================
% Ploting the results 
plot(x,gz(i),'r');

Answer 1

[Walter Roberson]

% Length of variable x and the Number of Entered data n

n = 11;

%===================================================
% Entered data

for i= 1:n
  x(i)=input('Enter measured point: ');
  z(i)=input('Enter depth: ');
  R(i)=input('Enter Raduis: ');
  rho(i)=input('Enter density: ');
end

gz = G*4*pi*R.^3/3.0.*z.*rho./(x.^2+z.^2).^1.5;

%===================================================
% Ploting the results 
plot(x,gz,'r');

Assuming that you defined G before this.